The present invention relates generally to passive microwave devices, and more particularly, to a symmetric Nxc3x97N branch-line hybrid power divider/combiner.
Microwave devices are generally divided into the broad categories of passive and active devices. Included under the heading of passive microwave devices are microwave hybrids and microwave couplers that are multi-port networks that are specifically configured for signal routing between the network ports. A device port into which power is normally fed is typically referred to as an incident port or an input port. A port from which power is extracted is called a coupled port or an output port and other ports (from which power is not extracted) are called isolated ports.
Microwave hybrids generally divide the power at each of a plurality of input ports transmit each of the divided portions to a respective one of a plurality of output ports and combine the transmitted powers at each output port. Accordingly, microwave hybrids are often called power divider/combiners. These dividers typically have 2n inputs and 2n outputs.
An example of a four-port (2xc3x972) power divider/combiner has two input ports and two output ports. In a perfect equal divider/combiner, the incident power at each input port would be divided into two equal portions which are each transmitted to a respective one of the output ports (i.e., the power division is perfect). None of the incident power would be reflected from the input ports and none of the power at any one of the input ports would be transmitted to the other input ports. This occurs only when the input ports are perfectly matched to their power sources and the isolation between input ports is perfect.
Although most conventional power divider/combiners successfully divide powers received at input ports and combine these divided powers at output ports, they typically include an excessive number of transmission-line members. Their use in microwave circuits, therefore, has a negative effect upon the size and weight of these circuits. This effect is emphasized when the hybrid""s transmission-line members are realized in waveguide or coaxial form and the effect is especially costly when such realizations are intended for weight-sensitive applications such as spacecraft.
An example of such a spacecraft application is an antenna array having a beam forming network which includes twenty two coaxial 8xc3x978 hybrid matrices (each hybrid matrix is formed with twelve 2xc3x972 hybrids) and interconnecting transmission lines. Power divider/combiners that can be realized with less transmission-line members and smaller size would present significant cost savings. Also, achieving symmetric Nxc3x97N (not 2nxc3x972n) branch-line hybrids will significantly reduce size and improve electrical performance.
It is, therefore, an object of the invention to provide an improved and reliable symmetric Nxc3x97N branch-line hybrid. Another object of the invention is to provide reduced cost while improving electrical performance.
In one aspect of the invention, a symmetric Nxc3x97N branch-line hybrid power divider/combiner has N input ports and N output ports. The divider/combiner divides received powers at each input port and transmits and combines the divided powers to the output ports. The divider/combiner includes N through transmission lines, each coupling a respective input port to a respective output port. The divider/combiner also includes N input branch transmission lines, each coupling a respective input port to a central input node and N output branch transmission lines, each coupling a respective output port to a central output node.
The present invention thus achieves an improved symmetric Nxc3x97N branch-line hybrid power divider/combiner. The present invention is advantageous in that it provides weight, volume and insertion loss advantages relative to conventional implementations. Additionally, the greater symmetry of these networks provide cost advantages due to simpler design, manufacture and test.
Additional advantages and features of the present invention will become apparent from the description that follows, and may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims, taken in conjunction with the accompanying drawings.